This program is designed to study the effects of chronic exposures to low levels of lead administered to fetal and infant rhesus monkeys. Two animal models of the lead exposure are under current study: (1) in utero exposure to lead throughout the entire period of gestation, and (2) neonatal exposure to lead, from Day 5-365 of life postpartum. The major objectives are to study behavioral effects through a broad battery of tests begun at 4 mo. of age and continued until year 3 of life. These behavioral measures include assessments of locomotor activity, motivational tests, social behavior, sensory function and cognitive tasks. These measures are supported by clinical chemistry to monitor the health and blood lead concentrations of the monkeys throughout the study. These data will reveal profiles of behavioral or neurobehavioral effects induced by lead toxicity, as well as those effects which persist long beyond normalization of blood and tissue lead burdens. Quantitative changes in behavior graphed versus blood lead burdens will be utilized to estimate threshold limit body burdens of lead ("no effect" levels of lead), where these thresholds appear to exist. These data will be important to a sound public regulatory policy relative to human exposure to lead, since neurobehavioral measures of damage from lead exposure occurring during periods of neural development can be expected to be one of the most sensitive endpoints for lead toxicity.